Charter flight in international air law has, from very beginning, not precisely defined by the International Civil Aviation Organization (lCAO) since 1947 when it came into being. By practice, the operation of charter traffic is, in its very beginning, the subject to the regulations of national rules and bilateral charter agreements (charter annex clause) within the framework of normal bilateral agreement of international air services. Taiwan had signed a series of bilateral air service agreement under the name of the Government of the Republic of China when Taiwan was recognized by the United Nations and major members of international community as the sole legal government representing China before 1971, but that situation was changed since then. Taiwan has only maintained diplomatic relations with 25 States, but maintained semi-official relations with major powers of the world. The former agreements were signed within the framework of the Vienna Convention on the Law of Treaties of 1969 while the latter agreements were signed within the framework of administrative and civil law of two countries which were not in the form of bilateral treaty signed by two sovereign States in its proper sense of international law. The legal regime of charter flights between Taiwan and Mainland China is regulated by special arrangements negotiated by delegated airlines and airlines association or private law institutions.